Upgrade the doc build process so that guide XML
is pre-processed, filtering include paths to point
to the correct common XML directory, and to be
aware of where guides are when files such as
appendices are shared between guides.
This facilitates building of translated guides,
which have a more nested directory structure
that broke assumptions about common assets.
All DocBook guides have been updated to use the
filtered path identifiers.
Also includes minor cleanup of commented out
legal info, tidy of the root node attributes,
inclusion of a Vim modeline, etc.
This change also retires the original build
infrastructure assets, which should be no problem
since all of the guides that continued to use these
have been updated to use the filtered paths that
point to the current infrastructre asset path(s).